Which of the following might reduce interference by an amateur station to a non-amateur over-the-air radio receiver?
Why Most interference to consumer receivers comes from fundamental overload: the amateur's clean, legal signal is simply so strong at the neighbor's antenna that the receiver's front end cannot reject it. The cure has to be applied at the receiver, where a filter (high-pass, band-reject or common-mode choke) at the antenna input keeps the out-of-band amateur energy from reaching the receiver's input stages. Once the strong signal is kept out of the front end, the receiver can handle the signals it was designed for.
Watch out Adding a filter at the transmitter only helps when the transmitter is actually radiating harmonics or spurious emissions; it does nothing for fundamental overload, because you cannot filter out the very frequency you are trying to transmit. Changing modes does not reduce the fundamental signal strength either.
Overload happens in the victim's receiver, so fix it there: filter at the receiver's antenna input.